The improvement in reliability, decrease in cost and realization of the lifesaving benefits of commercial and consumer smoke and carbon monoxide detectors have resulted in an increased installation of these devices in homes and businesses. Many homes now include at least one and typically multiple smoke detectors located throughout the residence. Indeed, many state laws require that apartment dwellings include at least one smoke detector within an apartment for single floor plan apartments, and at least one per floor for multi level apartments. Further, many state laws also require that smoke detectors be installed in homes prior to their sale.
Additionally, many homes and apartments are also being equipped with separate carbon monoxide detectors. The increase in installation of these detectors is due in large part to the improved reliability of these detectors which have, for the most part, overcome the false triggering of early devices. This increased use is also due in part to the recognition of people in colder climates that central heating systems, wood burning stoves, and fireplaces are all potential sources of deadly carbon monoxide which, without a carbon monoxide sensor, would go undetected until it was too late. A majority of these carbon monoxide detectors are being installed in dwellings which also include a separate smoke detector.
In recognition of the fact that many residences install both carbon monoxide and smoke detectors within the dwelling, Underwriters Laboratory (UL) has issued an industry standard to distinguish these two alarms. This UL standard requires that a fire/smoke alarm shall sound three (3) beeps at a rate of 0.5 second on, 0.5 second off with a gap between these three beep patterns of 1.5 seconds. The UL standard for CO alarms is similar, to wit four beeps at a rate of 0.1 second on, 0.1 second off with a gap between these four beep patterns of five (5) seconds. Since UL has issued these patterns as an industry standard, detector manufacturers must utilize them for each type of detector they make in order to gain UL approval.
The importance of being able to distinguish these two alarm patterns becomes apparent when the preferred actions for each alarm are compared. Specifically, a resident whose smoke detector has triggered is encouraged to close doors and windows, call the fire department to indicate that a fire has been detected, and immediately leave the dwelling. However, a resident whose carbon monoxide detector has triggered is encouraged to open doors and windows to allow fresh air to enter the dwelling to displace the carbon monoxide gas, and leave the dwelling for a period of time to allow the carbon monoxide gas to escape the dwelling. Some carbon monoxide detector manufacturers also recommend contacting a heating and cooling expert to check and clean the furnace, or alternatively their local fire department to indicate that high levels of carbon monoxide have been detected within their dwelling. Clearly, the preferred actions to be taken upon the detection of these two conditions vastly differ, and may result in a life threatening condition should one be mistaken for the other.
While the benefits of having both smoke detectors and carbon monoxide detectors installed within a dwelling far outweigh any problems associated therewith, problems which may become significant do exist. In addition to the above-described problem associated with the different courses of action to be pursued upon the detection of one of the two conditions, a similar situation may occur if both detectors trigger simultaneously. This situation may very well occur during an actual fire situation where the levels of smoke and carbon monoxide are typically high. In this situation, the sounding of both the carbon monoxide and the smoke detector alarms at the same time are most likely to cause confusion in the resident as to the cause and criticality of the situation. Precious seconds and minutes may be lost while the resident attempts to determine first what this new sound (the combination of the smoke and carbon monoxide detector alarms ringing simultaneously) is, and second, what action to take in response thereto. Therefore, this lack of coordination between the two alarm systems within the residence may lead to unnecessary confusion during a time of critical importance to the safety of the residents within the dwelling.